The present invention relates to an apparatus for applying photo resist on both surfaces of a semiconductor wafer, particularly to an apparatus for applying photo resist on both surfaces of a semiconductor wafer for obtaining a homogeneous photo resist layer.
In case of manufacturing integrated circuits or the like, the technique of so-called photo-etching has been used, and one process thereof involves the step of applying photo resist on the surface of a semiconductor wafer and drying it. Each process of photo-etching exerts an influence upon resolution of a pattern in an integrated circuit, so that in order to obtain an integrated circuit of good quality, it is necessary to uniformly apply and dry photo resist.
In order to manufacture silicone wafer as the material of a semiconductor wafer, a large amount of electric power is required, and as a result, silicone wafer becomes expensive. In order to effectively utilize such expensive silicone wafer these days, photo resist is applied to the back surface of the silicone wafer and a circuit is formed on both surfaces thereof.
Hitherto, for applying photo resist on both surfaces of a semiconductor wafer, a plurality of wafers have been accommodated in a cassette, the cassette being set at one end of a photo resist applying apparatus, and the wafers being successively supplied one by one from the cassette to the applying apparatus. One surface of the wafer has applied thereto dried photo resist by the applying apparatus and the wafer is successively accommodated in the cassette provided at the other end of the applying apparatus. These wafers are reversed and replaced in another cassette for applying photo resist to the rear surface of the wafer.
This reversed cassette is again set at one end of the photo resist applying apparatus, photo resist is applied to the rear surface of the wafer in the same process as described above, and then the photo resist applied wafer is accommodated in a cassette at the other end.
After this cassette is dried by putting in into a drier, an exposure operation is carried out in a succeeding apparatus exposing both surfaces.
As described above, the means for applying photo resist to both surfaces comprises a plurality of separate processes, takes trouble, and much time is taken between a process for applying photo resist on the front surface and a process for applying photo resist on the rear surface. Therefore, the quality of photo resist applied on both surfaces becomes uneven due to change of working surrounding or the like, during which interval dust which is highly deleterious in a semiconductor is adhered thereto.